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Physical sensor

a sensor and sensor technology, applied in the field of physical sensors, can solve problems such as difficulty in providing a structure, and achieve the effect of improving the spring characteristic and improving the spring characteristi

Inactive Publication Date: 2009-08-13
DENSO CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0016]The vertical beam and the horizontal beam are formed with different thicknesses. A spring characteristic of the vertical beam can differ from a spring constant of the horizontal beam. The beams can be individually assigned intended values. The height of the vertical beam is independent of the thickness of the oxide film since the silicon layer is removed at the bottom near the support substrate. The spring characteristic can be more improved. A physical quantity can be detected perpendicularly to the substrate based on deflection of the vertical beam having an improved spring characteristic. In addition, a physical quantity can be detected parallel to the substrate based on deflection of the horizontal beam having an improved spring characteristic.

Problems solved by technology

It is difficult to provide a structure that features an intended spring characteristic in each direction.

Method used

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first embodiment

[0046]The following describes a physical sensor according to the first embodiment. The embodiment represents application to a three-axis capacitance-detecting acceleration sensor that detects accelerations in three directions. FIG. 1 is a front view of the acceleration sensor according to the first embodiment. FIG. 2 is a cross sectional view taken along line II-II of FIG. 1. The acceleration sensor according to the embodiment will be described with reference to these drawings.

[0047]As shown in FIGS. 1 and 2, an SOI substrate 4 is used to form a sensor section of the acceleration sensor according to the embodiment. The SOI 4 substrate includes a support substrate 1, an embedded oxide film 2, and a silicon layer 3 that are layered in this order.

[0048]As shown in FIG. 2, the support substrate 1 is made of n-type silicon, for example. A lower electrode 5 doped with p-type impurities is formed over the surface of the support substrate 1 toward the silicon layer 3. The embedded oxide fil...

second embodiment

[0072]The second embodiment will be described below. The acceleration sensor according to the embodiment includes modifications to the first embodiment such as adding a cap and changing the manufacturing method of the acceleration sensor. The basic structure of the acceleration sensor is the same as the first embodiment.

[0073]FIG. 5 is a partially cross sectional perspective view of the acceleration sensor according to the embodiment. FIG. 5 is equivalent to a perspective view based on a cross sectional view taken along line V-V in FIG. 1.

[0074]As shown in FIG. 5, a cap 31 is provided on the surface of the SOI substrate 4. The cap 31 is shaped equally to the SOI substrate 4 and is made of an insulating material such as a non-doped silicon or glass substrate. The cap 31 is bonded to the SOI substrate 4 via the insulating film 32 around the outer edge of the cap 31. The cap 31 functions as a cover for the structures such as the movable section 6 and the fixed section 7 formed on the S...

third embodiment

[0085]The following describes the third embodiment. The acceleration sensor according to the embodiment includes modifications to the first embodiment such as changing the mode of detecting an acceleration in the vertical direction with reference to the substrate and accordingly changing the structure. The basic structure of the acceleration sensor is the same as the first embodiment.

[0086]FIG. 8 is a cross sectional view showing an acceleration sensor according to the third embodiment. FIG. 9 is a partially cross sectional perspective view of the acceleration sensor in FIG. 8. FIG. 9 is equivalent to a perspective view based on a cross sectional view taken along line V-V in FIG. 1.

[0087]As shown in FIG. 8, the acceleration sensor according to the embodiment does not include the lower electrode 5 shown in the first embodiment but includes the upper electrode 30 instead. The upper electrode 30 is shaped equally to the SOI substrate 4 and is arranged on the surface of the cap 31 made ...

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Abstract

A physical sensor includes: a substrate having a silicon layer, an oxide film and a support layer; and a sensor portion having movable and fixed electrodes and a lower electrode. The movable electrode is supported by a beam on the support layer. The fixed electrode faces the movable electrode. The lower electrode is disposed on the support layer and faces the movable electrode. The physical sensor detects horizontal physical quantity based on a capacitance between the movable and fixed electrodes, and vertical physical quantity based on a capacitance between the movable and lower electrodes. The beam includes vertical and horizontal beams. The thickness of the vertical beam is smaller than the thickness of the horizontal beam.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is based on Japanese Patent Applications No. 2008-31703 filed on Feb. 13, 2008, and No. 2008-247768 filed on Sep. 26, 2008, the disclosures of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to a physical sensor for detecting a physical quantity based on a capacitance between a movable electrode and a fixed electrode.BACKGROUND OF THE INVENTION[0003]A conventional physical sensor includes a fixed section and a movable section supported by a beam structure on a substrate. The movable section moves relatively to the fixed section in accordance with application of a physical quantity such as an acceleration or an angular velocity. Using this mechanism, the physical sensor detects the applied physical quantity.[0004]For example, in the method proposed in Patent Document 1, the movable section is formed as follows. An oxide-film sacrifice layer is sandwiched between upper an...

Claims

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Application Information

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IPC IPC(8): G01P15/125H01L21/28G01C19/56G01C19/5769G01P15/18H01L29/84
CPCG01P15/0802G01P15/125G01P15/18G01P2015/082
Inventor SUGIURA, KAZUHIKOISOBE, YOSHIHIKO
Owner DENSO CORP
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